GFX Technologies #3 - Through the Glass of GF Lenses

Since the official GFX 50S announcement on January 19, 2017, comparisons with various models have been made, and image quality of the GFX system has been a hot topic for debate in the street. Since the end of February, the camera is finally in stores, and discussion is getting even more heated. Whether these photographers read our articles or not, some are pointing out a difference in image quality "because sensors are different" or that "no, it is due to Fujiifilm's image processing".

The truth is, there are many factors that make up image quality, and since they are intrinsically intertwined, you cannot just break down the aggregate quality to one device or technology. Lenses are a huge factor that contributes to image quality. Lens technology is not everything, but there is a limit to what one can do post-processing if the lens used is mediocre. People see the difference in the result of medium format GFX, largely due to the lens.

Are the current medium format lenses in the industry the best in the world? Not quite. With the exception of a few, many of the lenses in the market are not designed with the latest technology in mind. The latest sensors have much greater potential than what these lenses can capture. Considering that sensor technology will continue to advance just as Moore's law indicates, it will be more evident in years to come.

So here is the reason why we are introducing the new GF Lenses with the new GFX camera system. The image quality of digital medium format can truly shine if the lenses are optimized for the latest (and future) technologies.

Let's be clear. It is unfair to compare GF Lenses directly with existing medium format lenses. The image quality of conventional medium format system was largely dependent on the size of imager. The granularity (= resolution) of the film remains the same even if the size changes, so bigger the film, the better the picture quality will be. However, imager has changed from film to CMOS sensor, and the resolution per unit area has improved. The 24MP APS sensor used for X Mount now has exceeded the resolution of 645 film. With lenses designed with film premises, it is fair to say that some of them will have insufficient performance.

Another reason is that there was no mount that could have realized ideal lens design. As previously mentioned, mirror boxes limit the freedom of lens designs. Lenses alone can be created, but there would be no associated mount that go with it.

G Mount solves that dilemma. G Mount incorporates mirrorless technology and high-pixel-count CMOS sensor so that an ideal lens design could be realized.

It is also important to note that the lens is optimally designed for the imager. The G Mount sensor has resolving power of that 4x5 large format with the mere size of 43.8x32.9mm. Rather than cropping the center of large format lenses, better images are delivered by optimal lens design for the image circle.

Designing is just a start for realizing high performance lenses. Lens designs that are too good on paper sometimes lack manufacturability. The design sensitivity becomes too high in such a case and the yield turns bad.

Such lens design only allows very small margin of differences; high precision assembling is required to deliver the intended performance

We put much higher cost and labor for GF Lenses than for that of a typical lens. We make sure that necessary adjustments are made with precision at every step. Some manufacturing processes are only possible with the GF Lens due to our overriding efforts. Lens designs were realized with that extra manufacturing care for the GF Lenses.

The result speaks for itself. You can have a look at the MTF chart, but know that lenses can resolve beyond what is on the chart. Aberrations are also minimized.

The GF Lenses can cope with a resolution up to 100MP. It means that the lens has a resolving power an image circle that is 4x larger than that of an APS lens. The MTF chart of GF Lenses comes with 40 lines per mm, which is higher frequency than 35mm format lenses, exactly our vision and goal for GF Lens performance.